Field of the Disclosure
The present disclosure, for example, relates to wireless communication systems, and more particularly to techniques for transmission of sounding reference signals in a shared radio frequency (RF) spectrum band and a dedicated RF spectrum band.
Description of Related Art
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UE) devices. A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
Some modes of communication may enable communication between a base station and a UE in a shared radio frequency (RF) spectrum band, or in different RF spectrum bands (e.g., in a dedicated RF spectrum band and a shared RF spectrum band) of a cellular network. However, in contrast to a carrier in a dedicated RF spectrum band, which may be allocated for use by the devices of one public land mobile network (PLMN) and be available to a base station or a UE of the PLMN at predetermined (or all) times, a carrier in a shared RF spectrum band may be available for use by the devices of the PLMN intermittently. This intermittent availability may be a result of contention for access to the carrier of the shared RF spectrum band, between devices of the PLMN, devices of one or more other PLMNs, and/or other devices (e.g., Wi-Fi devices). For some radio frames, a device of a PLMN may win contention for access to a carrier in the shared RF spectrum band, while for other radio frames, the device may not win contention for access to the carrier in the shared RF spectrum band.
Because of the intermittent availability of carriers in a shared RF spectrum band, base stations and UEs may use techniques that provide fairness in coexistence with other users of the shared RF spectrum band, and that still provide reliable communications. For example, such techniques may include transmitting some information or types of radio frames using the dedicated RF spectrum band and transmitting other information (e.g., lower priority information) or radio frames using the shared RF spectrum band. Such techniques may be referred to as License-Assisted Access (LAA), and it may be desirable in some systems to periodically adjust some parameters associated with one or both of the dedicated RF spectrum band or the shared RF spectrum band, in order to enhance system efficiency. Parameters may be adjusted based on one or more measurements related to channel quality, for example, that may be determined partly on a sounding reference signal (SRS) transmitted from a UE to a base station. In some deployments in which uplink transmissions may be transmitted using a shared RF spectrum band, a SRS may be transmitted using the shared RF spectrum band that may be used to estimate channel quality. Efficient techniques for transmitting a SRS in a shared RF spectrum band may enhance the operation of such networks.